1. Field of the Invention
The present invention relates to a wiring system for interconnecting vehicle-mounted electronic devices via a wiring harness and, in particular, to an improvement in the wiring system where a routing configuration of the wiring harness is simplified.
2. Description of Related Art
FIG. 5 shows a first example of a conventional wiring system that includes a vehicle-mounted device such as an electronic control unit (ECU) 1 for an electronic fuel injection (EFI) system. The ECU 1 has three ECU connectors A, B, C for connection to connectors a, b, c that are attached to leading ends W1, W2, W3 of an electric wire group W. However, wires of the electric wire group W, which are connected to the connectors a, b, c at one end, are configured to be dispersedly connected to different connectors e, f, g, h at the other end. In other words, wires that are equally connected to one connector at one end are dispersedly connected to different connectors at other ends. This is because an input signal is sent to the ECU through one wire, and an output signal is sent from the ECU through another wire.
As shown in FIG. 6, wires of an electric wire group W1 are connected to the connector a at one end, and are dispersedly connected to four different connectors e, f, g, h at other ends during subassembly. Wires of electric wire groups W2, W3 have the same configuration, except that they are not connected to the connectors e, f, g, h at the other end during subassembly.
More particularly, all the electric wire groups W1, W2, W3 are respectively connected to the connectors a, b, c at one end in advance during subassembly. However, only the electric wire group W1 is connected to the connectors e, f, g, h at other end during subassembly. The remaining electric wire groups W2, W3 are manually coupled to the connectors e, f, g, h subsequently, during final assembly. Arrows shown in FIG. 6 indicate terminals which are crimped at the other ends of the wires of the wire groups W2, W3 and which are mounted in the connectors e, f, g, h subsequently during final assembly. The wires are left hanging, and the terminals are left exposed until final assembly.
This presents the following problems, especially when the wires are long like the ones that are connected to the ECU 1 and that measure approximately 2000 mm-3000 mm.
When other ends of long wires are left scattered and hanging without being connected to connectors, the overall assembly is tedious and cumbersome to assemble, and exposed terminals at the other ends of the long wires are susceptible to damage. Also, it is difficult to insert the exposed terminals into a connector during final assembly because they are attached to the long wires.
Also, FIG. 7 (A) shows a second example of a conventional wiring system. A wiring harness W/H-1, produced by bundling a plurality of wires d, extends between devices K1, K2 to electrically connect them via connectors C1, C2 provided at opposite ends thereof. Connection terminals (not shown) are provided at connection areas K1a, K2a of the devices K1, K2. The respective connection terminals are independently and uniquely arranged so that the arrangement patterns of the connection terminals do not correspond to one another between the connection areas K1a, K2a. Thus, the wiring harness W/H-1 has wire crossovers, with the wires d intersecting with one another.
This makes the lengths of the wires d different. Thus, the wires d have to be measured and cut separately one by one, as shown in FIG. 7(B). After the wires d are measured and cut, terminals are attached to opposite ends of the wires d, and then inserted into predetermined cavities of the connectors C1, C2.
As described above, manufacturing the wiring harness W/H-1 as shown in FIG. 7(A) requires a very cumbersome and time-consuming process, which does not allow manufacturing costs to be reduced.
Additionally, FIG. 8 shows a third example of a conventional wiring system that includes a wiring harness W/H-2 produced by bundling a plurality of wires d. The wiring harness W/H-2 extends among devices K3, K4, K5 and switches SW1, SW2, and electrically connect them via connectors C3, C4, C5, C6, C7 provided at respective ends thereof. The devices K3, K4, K5 and switches SW1, SW2 share common circuits, so that joint connectors J1, J2 are provided to form joint portions S1, S2 in the wiring harness W/H-2.
Since these joint portions S1, S2 are required, an overall circuit configuration of the wiring harness W/H-2 is complicated and cumbersome. As a result, time-consuming, subsequent terminal insertion rate during final assembly increases, thereby decreasing efficiency in subassembly and thus deteriorating the merits of subassembly production. Further, it is difficult to introduce an automatic assembly machine that would improve assembly efficiency because of the cumbersome circuit configuration. Furthermore, as in the case of the wiring harness W/H-1 as shown in FIG. 7(A), the wires d of the wiring harness W/H-2 may intersect to form crossovers, depending on the requirements of connection terminals arranged at connection areas of the devices K3, K4, K5 and switches SW, SW2. This further complicates the problems of this wiring system.